Gang bonding interconnect tape for semiconductive devices and method of making same

ABSTRACT

A gang bonding interconnect tape for use in an automatic bonding machine for gang bonding of semiconductive devices is fabricated by depositing a series of electrically insulative support structures, such as rings of epoxy resin, onto a metallic tape, as of copper, there being at least one of said electrically insulative support structures for individual ones of the interconnect lead patterns to be formed in said metallic tape. The side of the metallic tape, opposite to the support structure, is photoetched with a series of interconnect lead patterns with individual ones of said lead patterns being etched in registration with individual ones of said electrically insulative support structures. The individual electrically insulative support structure, preferably in the form of a ring, is located in each of the lead patterns intermediate the central region thereof and the outer region thereof for supporting the individual leads thereof in circumferentially spaced relation.

BACKGROUND OF THE INVENTION

The present invention relates in general to gang bonding interconnecttape for use in automatic gang bonding machines for gang bonding ofsemiconductive devices and to an improved tape and method of makingsame.

DESCRIPTION OF THE PRIOR ART

Heretofore, gang bonding interconnect tapes, having a series ofinterconnect patterns formed thereon, have been used in automatic gangbonding machines to gang bond the individual semiconductive dies to theinner ends of the individual lead patterns and for subsequent bonding ofthe outer regions of the interconnect lead patterns to a lead framestructure. In one prior method of fabricating the gang bondinginterconnect tape, a 5 mil thick polyimide tape is coated on one sidewith a half mil thick layer of adhesive. The coated tape is then punchedto provide outer sprocket holes and then centrally punched to providethe personality holes, i.e., the hole in the central region of the leadpattern to receive the die. The tape is also punched with a ring ofapertures in the region of the outer lead bond to facilitate shearing ofthe interconnect lead pattern at the time of making of the outer leadbond to the lead frame structure. A 1.3 to 1.4 mil thick copper sheet ishot laminated over the adhesive coating to provide a laminated tapestructure. The copper is coated with a layer of photoresist, and exposedto images corresponding to each of the individual interconnect leadpatterns. The exposed tape is then developed, and etched to form theinterconnect lead patterns in the copper sheet.

The resultant tape is fed through a first automatic gang bondingmachines wherein the inner ends of the individual interconnect leads arethermal compression gang bonded to gang bonding bumps on thesemiconductive device. In this first bonding step, the semiconductivedevice is transferred to the tape. The tape is then fed through a secondautomatic bonding machine wherein the individual lead patterns aresheared out of the tape and thermal compression gang bonded at theirouter ends to the inner ends of a pattern of leads, such as a lead framestructure, printed circuit board or flexible circuit.

The problem with this first method of fabricating an automatic gangbonding interconnect tape is that the punching operations are relativelyexpensive in that the punches have only limited life and the polyimideis relatively expensive.

In a second method for fabricating an automatic gang bondinginterconnect tape, a half mil thick polyimide coating is cast onto oneside of a 1.3 to 1.4 mil thick copper tape. Next, the tape is coatedwith photoresist on both sides. The tape is then exposed simultaneouslyon both sides with different patterns of optical radiation, the copperside being exposed with patterns for the individual interconnect leadsand the sprocket holes, whereas the polyimide side is exposed withpatterns of radiation corresponding to the personality holes, thesprocket holes and the ring of perforations in the region of the shearline at the outer lead bond area. The polyimide side is then etched toprovide the personality holes, the sprocket holes and the outer leadperforations. Next, the copper side is etched to provide theinterconnect lead patterns, and the sprocket hole patterns. Theresultant tape is then used in an automatic gang bonding machine in thesame manner as previously described.

The problem with this latter method for fabrication of an automatic gangbonding interconnect tape is the cost of performing the two etchingsteps and, particularly, the etch of the polyimide side of the tape.

Therefore, it is desired to provide an improved method for manufactureof an automatic gang bonding interconnect tape which is less costly ofmanufacture and which avoids the multiple punching operations of thefirst method and the two different etching steps of the second method.

SUMMARY OF THE PRESENT INVENTION

The principal object of the present invention is the provision of animproved automatic gang bonding interconnect tape and method of makingsame.

In one feature of the present invention, a series of electricallyinsulative support structures are deposited onto a copper tape, therebeing at least one of said electrically insulative support structures orrings for individual ones of the interconnect lead patterns to be formedin the copper tape. A series of interconnect lead patterns is thenformed in the tape with individual ones of the interconnect leadpatterns being disposed in registration with individual ones of saidelectrically insulative support structures.

In another feature of the present invention the individual electricallyinsulative support structures are deposited onto the metallic (copper)tape by flowing the electrically insulative material through a patternedscreen onto the metallic tape.

In another feature of the present invention, the electrically insulativesupport structures are made of an electrically insulative materialselected from the group consisting of certain thermal setting andthermal plastics.

In another feature of the present invention, parallel rows of saidelectrically insulative support structures are deposited on the metallictape. Parallel rows of metallic interconnect lead patterns are etched inregistration with individual ones of the support structures. The tape isthen slit parallel to the individual rows for separating same intoindividual gang bonding tapes.

In another feature of the present invention the metallic tape is punchedat the outer edges thereof with a series of sprocket or locator holesutilized in subsequent steps of depositing the electrically insulativesupport structures on the tape and for use in exposing the photoresistcoating to the patterns of radiation corresponding to individual ones ofthe interconnect lead patterns and associated locator holes.

Other features and advantages of the present invention will becomeapparent upon a perusal of the following specification taken inconnection with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a metallic tape depicting the parallel rows ofelectrically insulative support structures deposited thereon,

FIG. 2 is an enlarged view of a portion of the structure of FIG. 1delineated by line 2--2,

FIG. 3 is a view similar to that of FIG. 1 depicting the step ofexposing the photoresist coated metallic tape to the patterns ofradiation corresponding to the individual interconnect lead patterns andlocator hole patterns,

FIG. 4 is an enlarged detail view of a portion of the structure of FIG.3 delineated by line 4--4,

FIG. 5 is an enlarged detail view of a portion of the structure of FIG.3 delineated by line 5--5,

FIG. 6 is a plan view of one of the individual automatic gang bondinginterconnect lead tapes after having been separated from the compositetape of FIG. 3,

FIG. 7 is an enlarged detail view of a portion of the structure of FIG.6 delineated by line 7--7,

FIG. 8 is an enlarged sectional view of a portion of the interconnectlead structure of FIG. 7 as bonded to a die and to an outer lead frame,

FIG. 9 is a sectional view of a semiconductor die bonded to a firstinterconnnect lead pattern which is in turn bonded to a secondsurrounding interconnect lead pattern of FIG. 10, and

FIG. 10 is a schematic plan view of an alternative interconnect tapeembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1 and 2, a 1000 foot roll of wrought copper sheethaving a weight of one ounce per square foot or a thickness of 1.3 to1.4 mils is slit into a 70 millimeter width to provide a copper tape 11.The copper tape 11 is preferably coated with copper phosphate or othermaterials, using conventional techniques, to promote adhesion of organicplastic materials to be subsequently applied to the copper tape. Thecopper tape is punched along opposite side marginal edges thereof withsprocket holes 12 to be utilized as locating holes. The holes 12 arespaced at 1.5 inch intervals along the length of the tape 11. The coppertape is then annealed and cleaned.

A pattern of electrically insulative support structures 13, such asrings, are then screened, as by screening, onto one face of the coppertape 11. In the screening process, the sprocket holes 11 are utilized aslocating holes for indexing the screening pattern so as to provideproper indexing for the pattern of support structure 13. In a typicalexample of the screening step of the process, the support structures 13are screened through a 3×3 inch screen pattern. The support structures13 are deposited to a thickness of between 0.5 mils and 2 mils. Theelectrically insulative screening material 13 should be compatible withbonding temperatures of approximately 400° C. for 0.1 second, have a potlife of 4 hours at 25° C., be flexible in thicknesses of 0.5 to 2.0mils, and have the electrical properties of a good dielectric. Suitableelectrically insulative support structure materials include thermalsetting plastic materials and thermoplastic materials. The thermalsetting plastic materials include, cycloaliphatic plastics withanhydride cure, low molecular weight bisphenol with anhydride cure, bothcycloaliphatic and low molecular weight disphenol with phenolic cure,silicon material such as silanol and vinyl containing siloxane curedwith an SIH siloxane, polyimide, polyamide, mixtures of polyimide andpolamide, phenolics, and diallylphthalate with peroxide cure. Suitablethermoplastic materials include polysulphone, polycarbonate, and ABS.The use of these materials should be compatible with the temperaturesencountered in subsequent bonding steps. Thus, for thermal compressionbonding where temperatures of 450° C. are encountered the aforecitedepoxy and polyimide materials are most suitable.

A suitable epoxy for use in the screening step of the process includesanhydride cured cycloaliphatic epoxy resin which is liquid at roomtemperature and which has a relatively low viscosity at 25° C., that is,a viscosity less than 500 centipose. The epoxy resin includes athixotroping agent to carry the viscosity from 500 to over 120,000centipose and to provide a low yield value. A suitable thixotropingagent includes 7 to 8% by weight of fumed silica treated with silane orsilazane so as to convert the silanol groups to trimethylsiloxy groups.This epoxy forms the subject matter of and is claimed in copending U.S.application Ser. No. 567,724 filed Apr. 14, 1975.Iadd., now U.S. Pat.No. 4,043,969 issued Aug. 23, 1977 .Iaddend.and assigned to the sameassignee as the present invention.

As an alternative to screening of the electrically insulative supportstructures 13 onto the copper tape 11 they may be applied by any one ofa number of conventional methods such as injection molding,electrostatic spraying through a mask, or by transfer from a sheet ofthe material to the copper sheet.

For screening, the thermal setting materials are suitable when theyinclude a suitable thixotropic agent. For electrostatic spraying througha mask, either the thermal setting materials or the thermoplasticmaterials may be utilized. For injection molding, either the thermalsetting or thermoplastic materials may be utilized. For transfermolding, the thermal setting materials are suitable.

A number of different formats may be employed depending upon the size ofthe die which is to be bonded to the interconnect lead patterns to beformed on the tape. More particularly, these support structures 13 arescreened onto the tape 11 in a number of parallel rows 14 extendinglongitudinally of the tape 11. The number of parallel rows 14 dependsupon the width of the individual tapes which are to be subsequentlyformed by slitting of the master tape 11.

One format corresponds to an individual tape width of 11 millimeters tobe utilized with a die size less than 60×60 mils, such pattern having apitch P of 0.1667 inch, where the pitch is the longitudinal spacingbetween the center of adjacent support structures 13 of a given row,there being five rows 14 of such support structures 13 in the 70millimeter width of the master tape 11. In such a case, a 3 inch lengthof the composite tape 11 will accommodate 90 support rings 13.

A second format corresponds to an individual tape width of 13.75millimeters for accommodating die sizes less than 90×90 mils, suchpattern having a pitch P of 0.214 inch and providing four rows 14 in the70 millimeter width of the master tape 11 and 56 die locations per 3inch length of the master tape 11.

A third format corresponds to an individual tape width of 16 millimetersto accommodate die sizes less than 200 mils by 200 mils, such patternhaving a pitch P of 0.300 inch, there being three rows of such supportstructures 13 for a 70 millimeter wide master tape 11. This third formatprovides 30 die locations per 3 inch length of the master tape 11.

After the support structures 13 have been deposited on the tape 11, thetape is cured in an oven in an atmosphere of nitrogen gas so as toharden the individual support structures 13. At this point the tape 11may be inventoried, if desired.

Next, the master tape 11 having the support structures 13 depositedthereon is cleaned of the adhesion promoting coating and any oxidesthereon by appropriate etching and then coated with an antioxidantcoating such as chromate to promote photoresist adherence. A number ofsuitable antioxidant coatings including chromate are disclosed andclaimed in copending U.S. application Ser. No. 582,634 filed June 2,1975.Iadd., now U.S. Pat. No. 4,188,438 issued Feb. 12, 1980.Iaddend.and assigned to the same assignee as the present invention. Thechromate antioxidant coating is applied to the copper tape 11 bycleaning the copper tape with hydrochloric acid and then immersing thecopper tape in a plating solution of chromic acid mixed with sulfuricacid, such mixture being 2.0% chromic acid to 8% full strength sulfuricacid to 90% deionized water by volume. The tape is immersed for 1 minuteat room temperature then removed, rinsed in deionized water and dried.In this process, a chromate antioxidant coating is deposited on thecopper surface to a thickness of between 10 and 100 angstroms.

Next, the composite tape 11 is coated on both sides with a positive typephotoresist coating of conventional type utilized in the semiconductorart.

Next, the side of the tape 11 which is opposite to that containing thesupport structures 13 is exposed to patterns 15 of optical radiation towhich the photoresist material is sensitive. The patterns 15 ofradiation are produced by a conventional 4×4 inch photo mask as utilizedin the semiconductor art (see FIGS. 3-5). The mask 16 has thereon anarray of patterns 15 corresponding to the individual interconnect leadpatterns to be formed in the copper tape 11. In a typical example, themask 16 exposes a three inch length of the tape 11. In addition to theindividual interconnect lead patterns 15, the mask contains patterns 17corresponding to sprocket holes 17' for each of the tapes which are tobe subsequently split from the master tape 11.

Due to a peculiarity of the automatic gang bonding interconnectmachines, the sprocket locator holes 17' for a given interconnectpattern 15 must be axially displaced along the tape from the particularlead pattern of interest by approximately 0.5 inch for the 11 mm, 0.642inch for the 13.75 mm and 0.6 inch for the 16 mm±≈0.0005 inch. Thus, inthe case of the 11 mm format the interconnect patterns 15 on the mask atthe leading edge thereof have their respective sprocket holes 17trailing by 0.5 inch as shown in FIG. 4. Similarly, at the trailing edgeof the mask 16 the pattern for the sprocket holes 17 lags behind therespective interconnect pattern 15 by 0.5 inch. Thus, the individualtape sprocket holes 17 are indexed to the respective lead portions 15via the mask 16 to a tolerance of ±0.0005 inch.

On the other hand, the mask 16 is indexed to the tape 11 by means of thesprocket holes 12 at the marginal edge of the master tape 11. Thesesprocket holes 12 can provide indexing of the mask 16 to the pattern ofinsulative support structures 13 to ±5 mils. At the overlap of one setof patterns 15 exposed on the tape 11 through the mask 16 to asubsequent set of patterns exposed through the mask 16 the overlaptolerance is ±5 mils as provided by the sprocket holes 12. However, theautomatic gang bonding machine has the capability of picking up orreleasing the individual tape to compensate for the up to ±30 mil jumpin spacing of the sprocket holes 17 at the overlap of two patterns. Themethod of indexing the lead patterns 15 to their respective locatorholes on the mask 16 and indexing the mask to the tape 11 via thesprocket holes 12 is disclosed and claimed in copending U.S. applicationSer. No. 593,477 filed July 7, 1975 .Iadd.(now abandoned) .Iaddend.andassigned to the same assignee as the present invention. Suitableautomatic gang bonding interconnect machines are the ILB and OLB ModelNo. 1-1000 manufactured and marketed by Jade Corporation ofPhiladelphia, Penn.

Next, the exposed photoresist coating is developed and removed byconventional methods. The copper tape 11 is then etched through theremoved portions of the photoresist coating. The etched copper tape isthen stripped of the photoresist coating to form the individualinterconnect patterns 15' and sprocket holes 17'.

Next, the composite tape 11 is slit into the appropriate number ofindividual tape strips 21, as shown in FIGS. 6 and 7, such slittingoccurring inbetween adjacent rows of sprocket holes 17'. The individualgang bonding interconnect tapes 21 include a series of virgin sprocketholes 17' along opposite marginal side edges thereof and a series ofgang bonding interconnect lead patterns 15' formed therein.

The individual patterns 15' are personalized to the particularsemiconductive die type to which they are to be bonded and each includesan array of ribbon-shaped leads 22 extending outwardly from a centralaperture 23 (personality hole) to an outer region 24 of the copper tape21. The marginal edge of the personality hole 23 is defined by the innerlip of the electrically insulative support structure 13 (ring) and thering 13 has sufficient radial extent to provide sufficient support forthe individual leads 22 and to hold the leads 22 in the desiredcircumferentially spaced position in electrically insulative relation.The inner ends of the leads 22 overhang the inner periphery of thepersonality hole 23 for bonding to gang bonding bumps on thesemiconductive die.

An annular gap 25 is defined between the outer periphery of theelectrically insulative support structure 13 and the inner lip of theframe portion 24. This gap 25 is provided to facilitate shearing of theindividual leads 22 at their outer regions at the time that theinterconnect lead pattern 15 is thermal compression bonded to the innerlip of the lead frame structure, as more fully described below withregard to FIG. 8.

After the individual tapes 21 have been separated from the compositetape 11 they are inspected and spliced together into long lengths as of1000 feet. The tape is then utilized in the conventional manner withconventional automatic gang bonding interconnect machines such as theaforementioned Jade Model No. 1-100. Briefly, in these automatic gangbonding interconnect machines, as shown in FIG. 8, a semiconductor die27, having a plurality, such as 14, gang bonding bumps 28 formedthereon, is indexed with an individual personality hole 23 by the gangbonding machine.

The gang bonding bumps typically have a height of between 1.0 and 2.0mils and are connected at their bases to patterns of intraconnectmetallization on the semiconductive die 27. The inner ends of the leads22 are thermal compression bonded to the gang bonding bumps 28 by thegang bonding tool, not shown, which presses the inner ends of the leads22 down against the upper surface of the gang bonding bumps 28. In atypical example the gang bonding tool is made of carbon and heated to atemperature of, for example, 550° C. and presses the inner ends of theinterconnect leads down against the gang bonding bumps with a pressureof approximately 8 grams per square mil for a time of approximately 0.2seconds. The gang bonding tool gang bonds 14 of such gang bonding bumpsto their respective interconnect leads 22 simultaneously.

The die 27 is held to a base support structure via a release wax and dueto the heating of the die by the thermal compression tool, the waxreleases the die and it is thereby transferred to the tape 21. The tape21 with the dies 27 attached thereto is fed through a second gangbonding machine which thermal compression bonds the outer portions ofthe interconnect leads 22 to the inner ends of a set of lead framemembers 29. For bonding the inner ends of the lead frames 29 to theouter ends of the interconnect leads 22, the thermal compression tool,not shown, is brought up against the lower side of the interconnectleads 22 for pressing the upper surface of the interconnect leads intoengagement with the lower surface of the lead frame structure 29. In atypical example, the temperature of the bonding tool for the outer leadbond is approximately 450° C. and is held in engagement with theinterconnect leads for approximately 0.15 seconds with a bondingpressure of approximately 25 grams per square mil.

As the thermal compression bond is made between the interconnect lead 22and the inner ends of the lead frame 29, the copper interconnect leadpattern 15' is sheared along a shear line 31 located just inside theouter marginal edge of the interconnect lead pattern 15'. In thismanner, the lead attached die 27 is transferred from the tape 21 to theleadframe structure 29.

The advantages of the automatic gang bonding interconnect tape 21 andthe method of fabricating same according to the present inventioninclude, reduction of manufacturing cost of the tape 21 and that themaster tape 11 with the support structures 13 affixed thereto is lesscostly to inventory than the prior tape systems. In addition, theindividual tapes 21 have virgin sprocket or locator holes 17' for use inthe inner lead gang bonding machine.

In an alternative embodiment of the present invention, see FIGS. 9 and10, a 70 mm wide copper tape 41, as of 2.6 mil thickness, is punchedwith sprocket holes 12 and treated with an adhesion promoting agent, asbefore described. Patterns of electrically insulative support structures13', such as rings, are screened, or otherwise applied, onto one face ofthe copper tape 41, as before described. The tape 11 is cured andetched, as before described, to define certain interconnect leadpatterns 42 which are to form lead patterns for making gang bondingconnections to the outer ends of respective ones of the interconnectleads 22, as previously bonded at their inner ends to the dies 27. Theinterconnect lead patterns 42, thus, take the place of the lead frame 29of the previous example and the dies 27 are transferred to the flexiblelead patterns 42 upon making of the gang bond between the outer ends ofthe inner interconnect lead patterns 22 and the inner ends of the outerinterconnect lead pattern 42. Thus the latter interconnect lead pattern42 is similar to a flexible printed circuit board and may be punchedfrom the tape 41 along outer shear lines 44 of the pattern for bondingor otherwise being interconnected to other electrical circuitry at theouter margin thereof.

In this latter embodiment, additional insulative structures, such as agrid pattern, are deposited at the time of depositing the insulativerings for further strengthening of the lead patterns located outside ofthe bonding area.

What is claimed is:
 1. In a method for fabrication of a gang bondinginterconnect tape for interconnecting a first pattern of leads and asecond pattern of leads, such interconnect tape having a series ofmetallic interconnectlead patterns thereon, individual ones of said leadpatterns including a plurality of ribbon-shaped metallic leads extendingoutwardly from an inner central portion of said pattern to an outerregion of said pattern and including an individual electricallyinsulative support structure interconnecting a plurality of saidribbon-shaped metallic leads in a region of said pattern intermediatesaid outer region thereof and said inner central region thereof, thesteps of:depositing a series of said individual electrically insulativesupport structures onto said metallic tape, there being at least one ofsaid individual electrically insulative support structures forindividual ones of said interconnect lead patterns to be formed in saidmetallic tape.
 2. The method of claim 1 including the step of, forming aseries of said interconnect lead patterns in said metallic tape,individual ones of said lead patterns being formed in registration withindividual ones of said electrically insulative support structures so asto locate individual ones of said electrically insulative supportstructures in a region of individual ones of said lead patternsintermediate said inner central region thereof and said outer regionthereof.
 3. The method of claim 2 wherein the step of forming saidseries of said lead patterns in said tape comprises the steps of,coating the side of said tape opposite to said deposited series ofelectrically insulative support structures with a photoresist coating,exposing the photoresist coating to a series of radiation images each ofsaid images corresponding to individual ones of said interconnect leadpatterns to be formed in said tape, removing the photoresist coating inthe exposed patterns, and etching the tape in the regions of the removedphotoresist coating to form said interconnect patterns therein.
 4. Themethod of claim 2 wherein the step of forming said series of said leadpatterns in said tape comprises the steps of, coating the side of saidtape opposite to said deposited series of electrically insulativesupport structures with a photoresist coating, exposing said photoresistcoating to parallel rows of radiation images, each of said imagescorresponding to individual ones of said interconnect patterns to beformed in said tape, removing the photoresist coating in the exposedpatterns, and etching said tape in the regions of the removedphotoresist coating to form rows of interconnect patterns therein. 5.The method of claim 4 including the step of slitting said tape in theregions thereof between and parallel to said rows of interconnectpatterns to slit the tape into a plurality of tapes each having a row ofsaid interconnect patterns thereon.
 6. The method of claim 4 includingthe step of, punching a series of locator holes in said tape prior tothe step of exposing said tape to said rows of radiation images.
 7. Themethod of claim 4 wherein said step of exposing said tape to said rowsof interconnect patterns includes the step of, exposing said tape torows of radiation images corresponding to rows of locator holes to beformed in said tape there being at least one such row of locator holeimages for each row of interconnect pattern images, and wherein the stepof etching the tape includes, etching said rows of locator hole imagesto form at least one row of locator holes for each row of saidinterconnect patterns formed in said tape.
 8. The method of claim 1wherein the step of depositing said series of electrically insulativesupport structures on said metallic tape includes the step of,depositing a series of individual electrically insulative support ringson said tape to serve as said series of support structures.
 9. Themethod of claim 1 wherein said tape is elongated and wherein the step ofdepositing said series of electrically insulative support structures onsaid metallic tape includes the step of, depositing rows of saidelectrically insulative support structures on said tape, said rowsextending generally in the direction of elongation of said tape.
 10. Themethod of claim 1 wherein said tape is made of copper.
 11. The method ofclaim 1 wherein said step of depositing said series of electricallyinsulative support structures on said tape comprises the step of,flowing an electrically insulative material through a patterned screenonto said tape as a series pattern of electrically insulative portions,and allowing the electrically insulative patterns to harden into saidseries of electrically insulative support structures. .Iadd.12. A methodof producing a metal-plastic composite lead frame device for integratedcircuit packaging, said lead frame device having a plurality ofcantilever metal leads held in fixed alignment near their free ends by amember of plastics material, comprising the steps of:perforating acontinuous web of metallic foil with a plurality of accurately spacedregistration apertures along at least one marginal edge thereof;depositing on a first side of said foil a pattern of thin, electricallyinsulating plastic meterial accurately aligned with respect to saidapertures, said pattern having lesser overall dimensions than said web;coating the opposite side of said foil with a photoresist material;imaging a lead frame pattern on said photoresist at accurately alignedpositions with respect to said apertures; developing said imaged leadframe pattern; and passing said strip through an etching bath wherebysaid strip will be etched away leaving only a lead frame with the leadssupported by said plastics material. .Iaddend. .Iadd.13. A methodaccording to claim 12 wherein said pattern of electrically insulatingplastic material is printed on said metal foil and has a thickness inthe range of 0.5 to 2 mils. .Iaddend. .Iadd.14. A method according toclaim 12 wherein said pattern of electrically insulating plasticmaterial is preformed and bonded to said metal foil. .Iaddend. .Iadd.15.A method according to claim 12 wherein said plastic material is selectedfrom the group including polyimides and epoxies. .Iaddend. .Iadd.16. Amethod according to claim 12 wherein said metallic foil is copper havinga thickness in the range of 1.3 to 2.6 mils. .Iaddend.